- The guess-rev.sh script is now a tweaked version of "setlocalversion" as
seen in Linux, U-Boot, and various other projects. When it finds source
control support (git, hg, svn) it uses IDs from there. Else (specific
to this project) it reports itself as "-snapshot", e.g. from gitweb.

I verified this new "guess-rev.sh" script runs under Cygwin.

- Also update the generic version strings to be like "0.3.0-dev" (during
development) instead of the very long "0.3.0-in-development". These also
show up in the PDF docs. For better tracking, we might eventually change
these strings to include the version IDs too.

- Change the startup banner version strings so they include the guess-rev
output. Development and release versions with GIT will be like